[Technical Field of the Invention]
The present invention mainly relates to a stator winding for use in a rotary electric machine, and, in particular, to such a stator winding which is preferably used in a vehicle alternator.
[Related Art]
A stator winding based on conventional art for use in a rotary electric machine is formed, for example, by bending linear conductors that are applied with insulation coating. In bending the linear conductors, the insulation coating is expanded in the outer surface of a curve which is formed by bending each of the conductors. As a result, the insulation coating is sometimes problematically damaged (e.g., refer to patent document JP-B-4506895).
In order to meet the recent needs of enhancing the performance of a rotary electric machine, a stator is required to increase the space factor in the slots. For this purpose, there is an increasing need of using a flat wire, as a material for forming a stator winding, which has a rectangular cross section. However, compared to a round wire having a circular cross section, a flat wire, when bent, causes a significant expansion in the insulation coating in the outer surface of the curve mentioned above, and accordingly has a high probability of suffering from damages in the insulation coating. Therefore, additional measures may have to be taken against this, such as increasing the thickness of the insulation coating of the flat wire, or reinforcing the insulation coating of the flat wire after being bent, or the like.
Further, from a standpoint of reducing cost incurred in the materials, only round wires may be purchased and rolled into flat wires only when used for a stator winding that is required to achieve a high space factor.
In this case, the coating characteristics will be impaired in the process of rolling the round wire into a flat wire. Therefore, the probability of damaging the insulation coating will become higher.